This invention relates to electrosurgery monitors and apparatus.
Electrosurgery apparatus, such as diathermy apparatus, employs high frequency RF energy to produce a surgical cutting or coagulation effect, or a combination of these effects. The energy is applied to the patient via a hand-held, patient electrode, which concentrates the energy in a small region so that the current density in that region is sufficiently high to produce the desired effect. Energy is returned to the electrosurgery unit via a large area, return electrode in the form of a flexible plate attached to the body. The large area of contact of the return electrode with the patient's skin ensures that the electrosurgery energy at the underlying skin surface has a much lower current density; in this way, no electrosurgery effect is produced at the return electrode.
A problem occurs with electrosurgery apparatus if the return electrode is not connected to the apparatus, since there will be no return path via the apparatus; this can lead to RF energy returning to ground via an alternative route. There is also a problem if the return electrode becomes loose, or if contact with the skin is reduced for some other reason, such as drying of the conductive gel used between the electrode and the skin; this can result in a more localized contact of the return plate with the skin. In both cases, a higher return current density may result, which in turn can produce burning of the skin.
In order to reduce the risk of burn injury to the patient, it is common practice for the electrosurgery apparatus to include some form of monitor to detect incorrect connection of the return electrode to the apparatus and separation of the return electrode from the skin. Because of the different forms that return electrodes can take, it can be difficult to provide a monitor that can be used safely with different return electrodes.